In response to the Ebola outbreak across West Africa, scientists around the world are racing to develop a vaccine against the disease. Now, a study by researchers from the National Institutes of Health reveals the creation of a vaccine that has generated long-term immunity against the Ebola virus in monkeys. The vaccine is now entering phase one clinical trials in humans.
Ebola is a severe viral illness characterized by sudden weakness, fever, muscle pain, headache and sore throat. It is caused by the genus Ebolavirus, which is a member of the Filoviridae family (filovirus).
Fatality rates during Ebola outbreaks are high. As of August 31st this year, the World Health Organization (WHO) state there have been an estimated 3,685 cases of Ebola virus and 1,841 deaths from the disease in West Africa, and the numbers are increasing.
There is currently no vaccine for the disease, but it is not through lack of trying. Medical News Today recently reported on a study from an international research team who has rapidly sequenced 99 Ebola virus genomes in an attempt to better understand the virus and find ways to contain it.
A recent report in the Annals of Internal Medicine - written by Dr. Scott Podolsky, associate professor of Global Health and Social Medicine at Harvard Medical School in Boston, MA - detailed how an experimental drug called ZMapp appeared to treat Ebola in two men who contracted the infection in Liberia.
ZMapp - which has only been tested in monkeys - has not yet been approved for public use by the US Food and Drug Administration (FDA).
Vaccine protected monkeys against Ebola virus for 10 months
In this latest study, published in the journal Nature Medicine, Nancy Sullivan, PhD, of the Vaccine Research Center at the National Institute of Allergy and Infectious Diseases (NIAID) and colleagues say they have developed a vaccine based on the chimpanzee-derived adenovirus vector (ChAd3) - a chimpanzee "cold" virus.
Past efforts to create a vaccine against Ebola have included the use of human adenoviruses. But the researchers explain that since a lot of humans have been exposed to these adenoviruses previously, their immune systems are set up to neutralize them.
As such, they decided to use chimpanzee adenoviruses that human immune systems have not come across before. Sullivan and colleagues tested ChAd3 in macaque monkeys.
They found that inoculation with ChAd3 alone provided short-term and limited long-term protection against Zaire Ebolavirus (EBOV) - one of the most common and deadly forms of the Ebola virus, and the one that is responsible for the majority of the latest Ebola outbreak.
However, the team identified a more effective vaccine regimen. First of all, the monkeys received ChAd3 that carried a gene called Ebolavirus Glycoprotein (GP). The team then inoculated the monkeys 8 weeks later with a vector called modified vaccine Ankara (MVA) that also carried the GP gene.
The researchers found that ChAd3 encoded with the GP gene, subsequently boosted by MVA encoded with GP protected the monkeys against EBOV for 10 months. The vaccine appeared to increase the number of T cells in the monkeys, which defended the immune system against the virus.
Commenting on their findings, the researchers say:
"We have demonstrated for the first time, to our knowledge, that both acute and durable immunity against EBOV can be achieved using a single inoculation (partial protection) or a prime-boost vaccine regimen (uniform protection).
This vaccine will be beneficial for populations at acute risk during natural outbreaks or others with a potential risk of occupational exposure."
Although this study assessed the vaccine's ability to protect against EBOV, the team believes it could also protect against another common form of the virus called Sudan Ebolavirus (SUDV) because the GP gene occurs in both.
As a result of these findings, the National Institutes of Health (NIH) recently announced that the vaccine will enter phase 1 clinical trials to test its effectiveness against EBOV and SUDV in humans.
Could the Ebola outbreak have been avoided altogether?
Meanwhile, a letter published in The Lancet claims the Ebola outbreak could have been avoided completely if international health systems had acted on recommendations given by a 2011 WHO Commission on worldwide health emergencies.
The committee proposed the introduction of a Global Health Emergency Workforce, supported by $100 million contingency fund in case of a public health emergency. WHO, however, did not take these recommendations on board.
Prof. Lawrence Gostin, faculty director of the O'Neill Institute for National & Global Health Law at Georgetown University in Washington, DC, says this caused a significant delay in WHO declaring a Public Health Emergency of International Concern for Ebola.
"If contingency funding were in place, WHO would have had a strong incentive to declare an international emergency in a timely way. WHO did not, however, act on the Review Committee's recommendations, even though the proposed surge capacity fund would be affordable - representing less than 0.5% of international health assistance."
Prof. Gostin says that the Ebola outbreak could have been averted if WHO had the funds to deal with it, and notes that this needs to be considered in order to prevent another epidemic, adding:
"A dedicated International Health Systems Fund at WHO would rebuild broken trust, with the returns of longer, healthier lives and economic development far exceeding the costs. This fund would encompass both emergency response capabilities and enduring health-system development.
"The West African Ebola epidemic could spark a badly needed global course correction that would favor strong health infrastructure. Sustainable funding scalable to needs for enduring health systems is a wise and affordable investment.
It is in all states' interests to contain health hazards that may eventually travel to their shores. But beyond self-interest are the imperatives of health and social justice - a humanitarian response that would work, now and for the future."